Directing the Rate-Enhancement for Hydronium Ion Catalyzed Dehydration via Organization of Alkanols in Nanoscopic Confinements

Manish Shetty, Huamin Wang, Feng Chen, Nicholas Jaegers, Yue Liu, Donald M. Camaioni, Oliver Y. Gutiérrez, Johannes A. Lercher

Research output: Contribution to journalArticlepeer-review

19 Scopus citations

Abstract

Alkanol dehydration rates catalyzed by hydronium ions are enhanced by the dimensions of steric confinements of zeolite pores as well as by intraporous intermolecular interactions with other alkanols. The higher rates with zeolite MFI having pores smaller than those of zeolite BEA for dehydration of secondary alkanols, 3-heptanol and 2-methyl-3-hexanol, is caused by the lower activation enthalpy in the tighter confinements of MFI that offsets a less positive activation entropy. The higher activity in BEA than in MFI for dehydration of a tertiary alkanol, 2-methyl-2-hexanol, is primarily attributed to the reduction of the activation enthalpy by stabilizing intraporous interactions of the Cβ-H transition state with surrounding alcohol molecules. Overall, we show that the positive impact of zeolite confinements results from the stabilization of transition state provided by the confinement and intermolecular interaction of alkanols with the transition state, which is impacted by both the size of confinements and the structure of alkanols in the E1 pathway of dehydration.

Original languageEnglish
Pages (from-to)2304-2311
Number of pages8
JournalAngewandte Chemie International Edition in English
Volume60
Issue number5
DOIs
StatePublished - 1 Feb 2021

Keywords

  • aliphatic alcohols
  • confinement effect
  • enthalpy-entropy compensation
  • hydronium ion
  • zeolites

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